Unfortunately, not sure if any official data been published by Malaysian government, but can do some guesses.
I think Singapore may have close to 2 million Malaysians working there, if not at least 1 million.
And then we count countries like UK, US, Australia, NZ, HK, Taiwan, China... should have at least another 1 million.
I am also guessing all of them 3 million malaysians will be earning much greater than our Malaysia's average income of around 5K rm. In fact, should be a lot more since we like to claim brain drain and better prospect.
So, lets say they can send back 2 months of their salary of say 10K rm min.
3 million x 10K x 2 month is like 60 billion ringgit.
Scary amount of remittance.
Disclaimer: all these are just my educated guesses.
Possibilities is there..
But the amount u stated is really big yo....
Until there's clear info on how many Malaysian overseas working... And real reason are known...
We can speculate only as for now...